There has been significant interest in methods for identifying and verifying various articles or products such as explosives, ammunition, paint, petroleum products, and documents. Known methods used to identify and verify generally involve adding and detecting materials like code-bearing microparticles, bulk chemical substances, and radioactive substances. Other methods used for identifying and verifying articles include those described in U.S. Pat. Nos. 6,030,657, 6,007,744, 6,005,915, 5,849,590, 5,760,394, 5,677,187, 5,474,937, 5,301,044, 5,208,630, 5,057,268, 4,862,143, 4,390,452, 4,363,965, and 4,045,676, as well as European Patent Application Nos. 0911626 and 0911627, the disclosures of which are incorporated herein by reference.
It is also known to apply materials to articles in order to track, for example, point of origin, authenticity, and their distribution. In one method inks, which are transparent in visible light, are sometimes applied to materials and the presence (or absence) of the ink is revealed by ultraviolet or infrared fluorescence. Other methods include implanting microscopic additives which can be detected optically. However, detecting these materials is primarily based on optical or photometric measurements.
Unfortunately, many of the apparatus and methods for identifying and verifying articles using such materials (called taggants) are unsatisfactory for several reasons. First, verification of presence or absence of the taggant is often difficult and time-consuming. In many instances, a sample of the article must be sent to an off-site laboratory for analysis. In other instances, the apparatus are often expensive, large, and difficult to operate. In yet other instances, the taggant used is radioactive, causing serious health concerns.
Preformed thermoplastic traffic marking materials for use on pavement, such as road surfaces, are important elements in modern traffic direction and control. They have been used, for example, in the form of arrows and lane dividers, as parking lot striping, to designate special areas, e.g., handicapped parking, and the like and are typically applied directly to the pavement surface. Application procedure consists of marking of the pavement, placing preformed signs on the surface and melting of the materials with propane torch or other heaters and providing a means for a strong bond between materials and pavement.
These materials must also follow strict regulation standards defining colors, content of polymer binder, glass beads, titanium dioxide, and mineral fillers. In addition these materials must comply with the requirements regarding leaching of toxic substances.
Preformed thermoplastic traffic marking materials are subject to a variety of factors that affect their performance and adherence to the pavement. Weathering, i.e., rain or snow, and high and low ambient temperature effects, high UV radiation from sun, can melt, crack or decompose the traffic marking material rendering it ineffective for the intended purposes.
Application and post-application procedures are required to provide sufficient durability. Uneven heating during application may result in insufficient penetration of melted material in the surface substrate and, thus, a weak bond between material and surface. These poorly heated areas are subject to cracks and material loss. Variation in production conditions and properties of the materials can also affect the melt characteristics of the materials and their adherence to the pavement surface.
Preformed thermoplastic pavement marking usually have a relatively long warranty of up to 5 years and more. When signs made of preformed thermoplastic materials fail they need to be replaced under the specified warranty to provide reliable traffic direction or control. Initial application to the pavement is usually provided by independent contractors selecting their materials from the list of approved suppliers. Since all materials must follow the same standards for color and reflectivity, once the pavement marking materials are applied to the pavement, it is practically impossible to determine the materials or manufacturer. Record keeping by the contractor may be marginal at best or partial wherein two or more vendor's products are used in a single project.
It is therefore important, under warranty claims, for the vendor of a pavement marking to be able to positively identify their product with a unique taggant after application and within the warranty period in cases of unacceptable wear or failure. Additionally, it is important to be able to determine production lots during root cause analysis of the problem.